This project investigates a possible new method of creating multichannel wireless interfaces to the nervous system which depends on the use of ultrasound energy as a means of power and communication with microsized implants. The approach employs implantable microdevices of approximately 1.5 mm x 3 mm in size potentially delivered to tissues through a syringe needle. These act as ultrasonically powered bioelectric transponders of extremely simple design. We will evaluate these for wireless recording of bioelectrical events in brain and for potential application to spine, nerve and muscle. The project depends on an unexpected process whereby actively driven carrier frequency from the skin experiences intermodulation by bioelectric events at the interface of an implanted semiconductor junction diode. Bioelectrical signals are encoded on a volume conducted carrier wave generated by an ultrasound pressure wave on an integrated piezoelectric polymer. Bioelectric waveforms are remotely recorded by demodulating volume conducted carrier waves to surface biopotential electrodes. We will investigate the potential for short range biotelemetry that appears to have the potential for large scale multichannel capability in combination with principles of transit time range determination common to ultrasound imaging systems. This approach suggests a technology leading to bioelectric waveform mapping using implanted microdevices as a type of transponder. Implant prototypes have been constructed using simple modifications of commercially available semiconductor devices powered by a small integrated piezoelectric element that is actuated by ultrasound energy emitted from a skin transducer. We will characterize its sensitivity, range, and other qualities in-vitro using tissue-mimicking saline tanks then progress to rat models to measure brain field potentials events at 2 KHz bandwidths. We will attempt to characterize and optimize the range and sensitivity performance of this approach for ultimate application to the more stringent conditions of human implantation. This work will give insight into the potential for ultrasound driven systems as a communications link for implantable neuroprostheses. Project success should allow investigators to adopt such technology in relatively short time frame using commercially available components and without the use of complex custom integrated circuitry for implants. This approach appears to hold the potential for dramatic reductions in size, weight, and complexity of neural interfaces and may enable a new generation of brain and nervous system recording devices. PUBLIC HEALTH RELEVANCE: This project investigates a possible new method of creating multichannel wireless interfaces to the nervous system which depends on the use of ultrasound energy as a means of power and communication with microsized implants. The approach employs implantable microdevices of approximately 1.5 mm x 3 mm in size potentially delivered to tissues through a syringe needle. These act as ultrasonically powered bioelectric transponders of extremely simple design. The research will examine the performance and sensitivity characteristics that might allow them to be used in large numbers in multichannel application for bioelectrical waveform mapping in the volume of tissues. The work has potential application to neurosprothestics for the brain, spine, sensory, and peripheral nervous systems. We will investigate the effectiveness of this passive telemetry technique for transmitting neurological signals by designing and testing a prototype device that fits inside of a rat skull. Developments of the principles might eventually allow new designs of neuroprostheses useful in a wide variety of rehabilitation, clinical diagnostic, and man-machine interface applications.